Whooping Cough Returns as Parents Skip Vaccines

Children who aren't vaccinated against whooping cough are 23 times more likely to develop the disease than children who get all of their shots on time, a new study shows.

Whooping cough, or pertussis, has been making a resurgence in recent years as more parents decide not to vaccinate their children, says Jason Glanz, author of a study in today's Pediatrics. In a study of 751 children enrolled in Kaiser Permanente of Colorado, one in 20 children who skipped the vaccine developed whooping cough, compared with one in 500 vaccinated children. In all, 11 percent to 12 percent of pertussis cases were in unvaccinated children.

Though more than 90 percent effective, the vaccine doesn't protect everyone, says Sean O'Leary, an infectious-disease fellow at Children's Hospital in Denver.

That's why vaccinating all children is crucial to creating "herd immunity" for the entire community, including newborns who are too young to be immunized, O'Leary says.

A study in the Pediatric Infectious Disease Journal in March found that 91 babies under age 1 died of whooping cough from 1999 to 2004. More than half were under 2 months old, the age at which infants get their first in a series of whooping cough shots.

Children can spread the bacteria if they don't receive their shots on schedule or if they miss any of the five required shots by age 5, says Glanz, a researcher at Kaiser's Institute for Healthcare Research and Department of Prevention in Denver. The vaccine's protection often wears off over time. So teens and adults can contract whooping cough, especially if they mistake their illness for a common cough or flu. Experts now recommend that children get a booster shot at age 11 and advise the parents of babies to get a booster as well, O'Leary says.

"Refusing to vaccinate your child not only puts your child at risk but puts susceptible children at risk," says O'Leary, who was not involved in the study. "We immunize ourselves and our children for the good of the community. By keeping those immunization rates high, we protect the vulnerable people out there."

Vaccines have eliminated killers such as polio, diphtheria and rubella. But because parents no longer see children dying of these once-common illnesses, some parents assume the diseases aren't dangerous, says pediatric infectious-disease specialist Janet Englund of Seattle Children's Hospital.

Some parents have refused vaccinations because of fear of mercury-based preservatives. But vaccines have been mercury-free since 2001, Glanz says.

Other parents space out vaccinations to avoid "overwhelming" a child's immune system. But Glanz says there's no evidence of such an effect. The Centers for Disease Control and Prevention bases its vaccine schedule recommendations on the results of clinical trials that have demonstrated their safety, he says.